It's only selfish if you're leading him on to believe something more could come out of your friendship. Let him know straight up that you have no romantic interest in him, and that you just want a platonic friendship. He may be super disappointed and upset by it, but the longer you wait to tell him, the more it's going to hurt him in the long run. How would you feel if you were in his shoes?

your girlfriend needs to grow up. if she doesn't know how to hold her liquor, she shouldn't be going out to clubs with people she barely knows while getting black out drunk. she's 29 years old for god's sake, she needs to act like it. you'll never really know the truth of what exactly happened that night, but either way, she should not be putting herself in that dangerous position. she obviously needs to mature the fuck up, or this shit will just repeat itself.